Process for promoting an oxide for use in a pyrotechnic composition

ABSTRACT

A process for increasing the heat of combustion of a metallic oxide to be used in a pyrotechnic composition comprising dissolving in water a metallic sulfate and a doping material which is a lithinum or zirconium compound and then calcining to form a doped metallic oxide.

Unite States atent Lipscomb, Jr. et al.

PROCESS FOR PROMOTING AN OXIDE FOR USE IN A PYROTECHNIC COMPOSITION Inventors: Charles A. Lipscomb, Jr., Crane, Ind.; Treva M. Smith, Hernando, Fla.

The United States of America as represented by the Secretary of the Navy, Washington, DC.

Filed: Aug. 21, 1972 Appl. No.: 282,508

Assignee:

U.S. c1 252/186, 149/20, 149/37 1111. C1..... C06b 15/00, COlg 9/02, 001 g 49/06 Field 61 Search 252/ 186; 149/20, 37, 19.1;

References Cited UNITED STATES PATENTS 8/1949 11611 et al 149/30 Douda 149/37 Primary Examiner-Carl D. Quarforth Assistant Examiner--lr'win Gluck Attorney, Agent, or Firm-R. S. Sciascia; Paul S.

Collignon [57] ABSTRACT A process for increasing the heat of combustion ofa metallic oxide to be used in a pyrotechnic composition comprising dissolving in water a metallic-sulfate and a doping material which is a lithinum or zirconium compound and then calcining to form a doped metallic oxide;

5 Claims, 2 Drawing Figures PATENTEflJunze I974 I I 3,821,120

HEAT OF COMBUSTION CAL/GM I I I I I I 500 600 700 800 900 I000 I IOO F8 0 PREPARATION TEMPERATURE IN DEGREES C.

Fig.1

HEAT OF COMBUSTION -CA| /GM 00 ZIRCONIUM DOPED I I O I 2 3 4 5 WEIGHT /o LI AND ZR DOPANT IN F6 0 Fig.2

PROCESS FOR PROMOTING AN OXIDE FOR USE IN A PYROTECHNIC COMPOSITION CROSS-REFERENCE TO RELATED APPLICATION US. Pat. application of Charles A. Lipscomb, Jr. and Treva M. Smith entitled, Pyrotechnic Composition Providing Increased Heat of Combustion, Ser. No.

281,582, filed Aug. 17, 1972.

BACKGROUND OF THE INVENTION The present invention relates to a method of increasing the heat of combustion of an oxide which is to be used in a pyrotechnic composition.

Pyrotechnic devices are widely used by military personnel and contain combustible chemicals which, when ignited, generate a flame, flash, infrared radiation, smoke or sound display, or combinations of these-effects, for a broad variety of purposes. Many devices, particularly the smoke and illuminating devices, are comprised of a fuel, an oxidizer and a binder.

Many of the recent improvements inpyrotechnic devices, such as flares, have been centered on providing an improved binder system. For example, in U.S. Pat. No. 3,41 1,964, which issued Nov. l9, 1968, to Bernard E. Douda, there is disclosed an illuminating flare composition comprised of a fuel, an oxidizing agent and a binder comprised of an epoxy resin and a polyglycol resin. Little, if any, work, has been done on improving an oxidizer for use in a pyrotechnic composition.

SUMMARY OF THE INVENTION The present invention relates to a process for increasing the heat of combustion of a metallic oxide to be used in a pyrotechnic composition. In particular, the present invention provides a method to increase the heat of combustion of zinc oxide and ferric oxide which is to be used in pyrotechnic munitions such as red phosphorus smokes and hygroscopic chloride (I-IC) smokes.

A metallic sulfate, such as ferric sulfate or zinc sulfate is dissolved in boiling distilled water to which about I to 5 percent, by weight, of a doping material has been added. The doping material is a compound of either lithium or zirconium. The solution is boiled until it becomes pasty in consistency and then the pasty solution is calcined at a temperature of between 600 and l,0O0 C. to form a doped metallic oxide.

It is therefore a general object of the present invention to provide a process for increasing the heat of combustion of a metallic oxide to be used in pyrotechnic compositions.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a graph showing the effect of preparation temperature on heat of combustion of ferric oxide; and

FIG. 2 is a graph showing the effect of the percentage of dopant on heat of combustion of ferric oxide.

DESCRIPTION OF THE PREFERRED EMBODIMENT In preparing a metallic oxide according to the present invention, preweighed amounts of metallic sulfate and.

the selected dopant are dissolved in distilled water. The metallic sulfates which have been successfully used are ferric sulfate, ferrous sulfate and zinc sulfate and the doping materials which have been used successfully are lithium hydroxide, lithium nitrate, zirconium sulfate and zirconium nitrate. The solution is heated to boiling, and heat is maintained until a persistent froth forms and the solution becomes very viscous. The solution is then transferred to crucibles and heated in a furnace at a temperature of between 600 and 1,000 C. for between 24 and 100 hours until calcining is complete. The remaining water is quickly driven off at this temperature, and the doped metallic sulfate decomposes to doped metallic oxide. It is necessary to periodically disturb the contents of the crucible to permit adequate venting of sulfur dioxide and steam decomposition products. The crucible and contents are then removed from the furnace and allowed to stand until cooled to ambient conditions. The metallic oxide is made up largely of loosely agglomerated fine particles having a size of about 0.5 to 1.0 microns and these agglomerates can be broken up with a mortar and pestel, by screening','or by other appropriate methods.

I EXAMPLE I 99 grams of zinc sulfate'and 1 gram of zirconium sulfate were dissolved in l00 ml of boiling distilled water. The solution was stirred and heated until the solution was reduced to 40 ml and was pasty in consistency. The pasty solution was calcined in a crucible at 700 C. for about 100 hours. The contents of-the crucible were stirred'several times'during the calcining process to permit venting of sulfur dioxide and other gaseous products. The final material produced was white in color and had an absolute density of 5.94 gm/cm, as compared with 5.58 gm/cm for unpromoted zinc oxide.

EXAMPLE II 99 grams of ferric sulfate and l 'gram of zirconium sulfate were dissolved in 300 ml of distilled water and the solution was boiled until a persistent froth forms and the solution became very viscous at a volume of between and ml. This viscous solution was then stored under refrigeration at a temperature of 45 F. for l8hours. The solution was then transferred to crucibles and placed in a furnace at atemperature of 600 C. for 24 hours. The remaining water was quickly driven off and the doped ferric sulfate decomposed to doped ferric oxide. The contents of the crucible were periodically disturbed to permit adequate venting of sulfur dioxide and steam decomposition products. The crucible and contents were then removed from the furnace and cooled at ambient room temperature. The Fe- O was fine particles of between 0.5 and 1.0 micron in size and was loosely agglomerated. The agglomerates were broken up by screening.

Referring to FIG. 1 of the drawing, it can be seen that the temperature used in preparing the doped ferric oxide has a noticeable effect on the heat of combustion when mixed with titanium and reacted. The reaction thatoccurs is:

It can be seen that ferric oxide prepared at a temperature of 600 C. has a heat of combustion of about 1,000 cal/ gm, while ferric oxide prepared at a temperature of 1,000 C. has a heat of combustion of only about 620 cal/gm.

Referring now to FIG. 2 of the drawing, there is shown the effect of dopant concentration on the heat of reaction that occurs in the chemical equation (1) shown above. When no dopant is used, the heat of combustion is about 760 cal/gm (Preparation temperature of about 800 C.). As the percent of doping material is increased, the heat of reaction increases. With a l percent lithium doping material, the heat of reaction is about 850 cal/gm and, for 5 percent, the heat of combustion increases to about 1,100 cal/gm. For corresponding l and 5 percent of zirconium doping material, the heats of combustion are about 780 cal/gm and 1,050 cal/gm, respectively.

it is recognized that various changes may be made to the process of this invention, and that ingredients other than those specifically described herein may be employed in its practice without departing from the spirit and scope of the invention.

We claim:

1. A process for promoting a metallic oxide for use in a pyrotechnic composition comprising,

dissolving in distilled water between about 95 and 9 9 parts by weight of a metallic sulfate selected from the group consisting of ferric sulfate, ferrous sulfate, and zinc sulfate and between about 1 and 5 parts by weight of a doping material selected from the group consisting of lithium hydroxide, lithium nitrate, zirconium sulfate and zirconium nitrate,

then heating the solution containing the metallic sulfate and doping material until the solution becomes pasty in consistency, and

then calcining at a temperature of between about 600.

and 1,000 degrees C. toproduce a doped metallic oxide.

2. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim I wherein said metallic sulfate is ferric sulfate and said doping material is zirconium sulfate.

3. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is zinc sulfate and said doping material is zirconium sulfate.

4. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic-sulfate is'ferric sulfate and said doping material is lithium hydroxide.

5. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is ferric sulfate and said doping material is lithium nitrate. 

2. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is ferric sulfate and said doping material is zirconium sulfate.
 3. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is zinc sulfate and said doping material is zirconium sulfate.
 4. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is ferric sulfate and said doping material is lithium hydroxide.
 5. A process for promoting a metallic oxide for use in a pyrotechnic composition as set forth in claim 1 wherein said metallic sulfate is ferric sulfate and said doping material is lithium nitrate. 